An impedimetric biosensor for real-time monitoring of bacterial growth in a microbial fermentor

In this paper, we describe an in situ sensor for estimating bacterial concentration in a lab-scale fermentor using impedance spectroscopy. We constructed the impedimetric biosensor using a gold-coated silicon wafer, PDMS polymer, and a borosilicate glass tube. An advantage of using these materials was that we could make a plug-type, disposable electrode. We compared the impedimetric differences between bacterial cells, culture media, and metabolic by-products. We measured real-time impedance changes of an E. coli solution at 0.01 MHz frequency of applied AC for 13 h, and correlated them with the bacteria concentration as estimated by a hemocytometer. In conclusion, impedance increased and reactance decreased during the measurement period, as the concentration of E. coli increased. The correlation between the E. coli concentration and the impedimetric data was linear.